What is the role of the phenomenon of ‘original antigenic sin' in immunity to this virus?
What will be an ideal response?
The phenomenon of ‘original antigenic sin' means that when a person is reinfected with a new strain of influenza virus that shares some epitopes with the virus they were first infected by, they will make an immune response (which will be a secondary immune response) only to the shared epitopes and not to the new epitopes. This is because when the virus binds via a new epitope (say HA*) to the B-cell receptor of a HA*-specific naive B cell, preexisting IgG antibodies against other epitopes on the virus can bind via their Fc regions to FcγRIIB1 receptors on the surface of the same cell. Cross-linking of the B-cell receptor and Fc receptor delivers an inhibitory signal to the B cell, thus blocking the production of a HA*-specific antibody response. As an influenza virus undergoes antigenic drift, some HA and NA epitopes change while others remain the same, so the person retains some immunity. However, when a completely new HA or NA is produced as a result of antigenic shift, and it shares no epitopes with the original antigens, the body sees the virus as a completely new infection, and disease results while the body is making a new primary response against the virus.
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Each positive acute phase reactant below is paired correctly with its function except
A) alpha-1-antitrypsin/neutralize elastase released by neutrophils. B) C-reactive protein/opsonin and complement activation. C) complement/group of proteins that when activated can lyse target cells. D) fibrinogen/activation of fibroblast cells. E) haptoglobin/binds free hemoglobin and transports it to the liver.
A cocarcinogen is a substance that is known to cause cancer.
Answer the following statement true (T) or false (F)
It is becoming increasingly more important to devote attention to valuing and assessing the product of physical activity
Indicate whether the statement is true or false
At 50 percent training intensity, the recommended duration of cardiorespiratory training for a reasonably conditioned adult is ____ minutes per session
a. 15 to 20 b. no more than 45 c. about 30 d. about 60 e. no less than 90